Method: For the dough, in a bowl combine together flour, baking powder and sugar. Add butter and mix well; then add yogurt or sour cream. Transfer dough to refrigerator for 30 minutes. For the filling just mix all ingredients. Preheat oven to 180 degrees C. Line baking tray with parchment paper. Divide chilled dough in half. Place each half of the dough between 2 pieces of waxed paper and roll out into thin sheet. Sprinkle with cocoa filling and roll with hands using wax paper as support to oblong roll. Cut into 0.5-1 cm thick slices and place on the baking tray. Bake for about 15-20 minutes or until done.